SL- geophysical hazards

Question 1

what are convection currents?

Answer 1

flowing fluid that is moving because there is a temperature or density difference within the material
- occur in the earth’s interior
- there is constant movement
-

Question 2

what is the cause of the movement of convection currents?

Answer 2

• cause of the movement is the radioactive decay of uranium and potassium in the mantle

Question 3

what are seismic vibrations?

Answer 3

waves of energy that travel through the earth’s crust, and to the surface

Question 4

what can larger earthquakes have (seismic waves)?

Answer 4

can have foreshocks and aftershocks which are both smaller tremors

Question 5

why can aftershocks be devastating?

Answer 5

because the buildings are already damaged so when the aftershocks come they are more prone to collapse `

Question 6

what is the focus?

Answer 6

the point inside the earth where the earthquake originates

Question 7

what does a shallow earthquake mean?

Answer 7

Shallow focus earthquakes occur with greater potential to do damage as less of the energy by the earthquake is absorbed by overlying material

Question 8

what is the epicentre?

Answer 8

the point above the focus

Question 9

what factors impact the geophysical events?

Answer 9

Magnitude + frequency
population density
type of buildings
time of day
distance from the event
types of rock and sediment

Question 10

why does magnitude and frequency impact geophysical events?

Answer 10

higher M has more impacts and is more powerful

Question 11

why does population density impact geophysical events?

Answer 11

• More damage in urban areas that are population dense
  
  • More building density when there is population density

Question 12

why does the type of buildings impact geophysical events?

Answer 12

• High income countries generally have better quality buildings
  Meaning they recover faster and will have less damage to begin with

Question 13

why does time of day impact geophysical events?

Answer 13

• Rush hour will cause more deaths
  Asleep at night meaning there are more people unaware

Question 14

why does the distance from the event impact geophysical events?

Answer 14

The closer the city is to the focus the more impact

Question 15

why do the types of rock and sediment impact geophysical events?

Answer 15

• Loose materials may act like liquid when shaken, known as liquification
  
  • Solid rock is safer
  • Buildings built on flat areas are safer
    Volcanic sediments are at high risk of landslide

Question 16

what is vulnerability defined as?

Answer 16

Defined as the characteristics and circumstances of a community, system of asset that make it susceptible to the damaging effects of a hazard

Question 17

how do you calculate the vulnerability/risk?

Answer 17

RIsk = hazard x exposure x vulnerability

Question 18

what is risk defined as?

Answer 18

risk or disaster risk is expressed as the likelihood of loss of life, injury or destruction and damage from a disaster in a given period of time.

Question 19

what is the other equation for calculating risk?

Answer 19

Risk = hazard x vulnerability / capacity (means to respond to an event)

Question 20

what are the characteristics of a shield volcano?

Answer 20

• composed of basaltic magma
• lava eurputed is runny and non-acidic
• gentle side slopes
• less violent eurputions
• found on divergent plate boundaries

Question 21

what are the characteristics of a composite volcano?

Answer 21

• cone shapes / steep sides
• very very large
• composed of layers of ash and acidic lava flows
• pyroclastic flow
• can be active over a long time
• thick, highly viscous lava
• found on divergent plate boundaries

Question 22

what are the characteristics of a cone volcano?

Answer 22

• simple volcanoes
• cone shaped due to build up of layers of lava flows
• single opening for lava
• single crater vent
• found on constructive plate boundaries

Question 23

what human thing can trigger an earthquake?

Answer 23

• fracking
• mining
• dam building

Question 24

how does fracking trigger earthquakes?

Answer 24

• Waste water produces by wells that were hydraulic fractured can cause induced earthquakes when its injected into deep water wells
  
  • Waster water injection can raise pressure levels in the rock formation over much longer periods of time and over larger areas than hydraulic fracturing does.
  • Primarily caused by disposal of waste fluids that are a byproducts of oil production.

Question 25

how does mining trigger earthquakes?

Answer 25

• The extraction of resources refers to the withdrawing of materials from the environment for human use, including fossil fuels (oil, gas, and coal), rocks and minerals, biomass via deforestation and fishing and hunting, and water. The removal of material from the earth can cause instability, leading to sudden collapses that trigger earthquakes.
• mining accounted for the highest number of human-induced earthquakes worldwide (many earthquakes clustered around 271 sites).

Question 26

how does dam building trigger earthquakes?

Answer 26

The higher water levels created greater pressure in pore spaces in rocks at lower depths, a known trigger for earthquakes. This is the same effect that can lead to earthquakes when wastewater is pumped into the ground.

Question 27

what is liquefaction?

Answer 27

When loosely packed, water-logged sediments at or near the ground surface lose their strength in response to strong ground shaking (earthquakes) basically when water is in the sand and there is shaking of the particles, buildings on it will exert pressure and the sand and water mixture will act as a liquid because water cant be compacted but the sand can. When it acts like a liquid things will sink into it.

Question 28

what is a tsunami?

Answer 28

A tsunami is a series of extremely long waves caused by a large and sudden displacement of the ocean, usually the result of an earthquake below or near the ocean floor.

Question 29

how is a landslide a secondary hazard of an earthquake?

Answer 29

the transmission of seismic waves can cause shaking and vibration of ground surface. This often trigger the collapse of potential landslide areas, which is known as earthquake-induced landslide.

Question 30

what is a conservative margin?

Answer 30

At a conservative plate margin, the plates move past each other or are side by side moving at different speeds. As the plates move, friction occurs and plates become stuck. Pressure builds up because the plates are still trying to move. When the pressure is released, it sends out huge amounts of energy, causing an earthquake

Question 31

What’s a constructive plate margin?

Answer 31

At a constructive plate margin the plates move apart from one another. When this happens the magma from the mantle rises up to make (or construct) new land in the form of a shield volcano. The movement of the plates over the mantle can cause earthquakes.

Question 32

what is a destructive plate margin?

Answer 32

happens when continental and oceanic plates move toward each other. the more dense oceanic plate is forced underneath the other plate. the oceanic plate then melts as it sinks below due to friction in the subduction zone (convection currents). the molten crust rises which causes a volcanic eruption.

movement of the plate isn’t smooth so pressure can build up and cause an earthquake

Question 33

what does a destructive plate boundary form?

Answer 33

fold mountains as the plate is crumpled by the pressure.

Question 34

what is a collision or convergent plate boundary?

Answer 34

when two plates of similar density collide into each other due to the compression of the two plates. tall mountain ranges usually produced. the two plate boundaries crashing together and going up causes pressure build-up which then gets released and makes an earthquake

Question 35

how can you predict tectonic hazards

Answer 35

satellites
seismographs
direct measurements

Question 36

what are primary effects of an earthquake?

Answer 36

liquefaction
landslides

Question 37

what are secondary effects of an earthquake?

Answer 37

injury/deaths
fires

Question 38

plate boundaries and volcano types

Answer 38

Most subduction-related volcanoes are explosive and build stratovolcanoes, while rift volcanoes tend to be more effusive and build shield volcanoes

Question 39

case study for mass movement

Answer 39

italy- ponzano
2017 very slow movement - cause by 2 meters of soil melt and intense rain fall
impacts were not the best
sierra leone mudslides
- killed 1000 ppl
caused by monsoon season
soil erosion
weakened by buildings
LIC so hospital is overwhelmed